You need to find the value of b so solve the first equation in terms of x:

b + x = -9
x = -9 - b

then substitute the result (-9 - 1b) into the second equation:

-b + 3(-9 - b) = -9
-b + (3 x -9) + (3 x -b) = -9
-b - 27 - 3b = -9
-b - 3b = -9 + 27
-4b = 18
b = \( \frac{18}{-4} \)
b = -4\(\frac{1}{2}\)

Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).

For parallel lines with a transversal, the following relationships apply:

• angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°)
• alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°)
• all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other
• same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°)

Applying these relationships starting with x° = 161, the value of b° is 161.

To multiply binomials, use the FOIL method. FOIL stands for First, Outside, Inside, Last and refers to the position of each term in the parentheses:

(y - 7)(y + 7)
(y x y) + (y x 7) + (-7 x y) + (-7 x 7)
y² + 7y - 7y - 49
y² - 49

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(5a)(2ab) - (2a²)(5b)
(5 x 2)(a x a x b) - (2 x 5)(a² x b)
(10)(a¹⁺¹ x b) - (10)(a²b)
10a²b - 10a²b
0a²b